Kozue Ichimura is a 48-year-old housewife whose relationship with her busy husband is limited to occasional phone sex. One day, while engrossed in phone sex, she is caught by her son. Intrigued, he begins touching her between the legs. The pleasure, combined with the joy of finally experiencing what she had secretly desired, overwhelms her. This becomes their shared secret, giving rise to a new, forbidden relationship between mother and son.